1. Field of the Invention
The present invention relates to a sheet processing apparatus including an aligning member that aligns sheets on a tray.
2. Description of the Related Art
A sheet processing apparatus is used, for example, by being coupled to an image forming apparatus. The image forming apparatus forms an image on sheets. The sheet processing apparatus is configured to, after receiving the sheets in a process tray as a stack tray, collate the sheets into a bundle form, and perform a stitching operation for such bundle of the sheets by a staple mechanism as processing means. In the event of performing the stitching operation, the sheet processing apparatus conveys the sheets onto the process tray by conveyance rollers as a sheet conveyance unit that conveys the sheets thereonto, and aligns the sheets by hitting the sheets against sheet edge regulating means by using a return roller as an aligning roller. After that, the sheet processing apparatus performs the stitching operation by the staple mechanism. Here, in the vicinity of the sheet edge regulating means, the return roller is arranged so as to be movable up and down by switching means. The return roller is lowered to a contact portion thereof that abuts on the sheets, the sheets are conveyed toward the sheet edge regulating means by the aligning roller, and leading edges of the sheets are hit against the sheet edge regulating means. In such a way, an operation of aligning the sheets is surely performed (refer to Japanese Patent Application Laid-Open No. 2006-82153 and Japanese Patent Application Laid-Open No. H05-169396).
However, in the event of allowing the aligning roller to perform such aligning operation for the trailing edges of the sheets as described above, in some case, the aligning operation for the sheets is not smoothly performed depending on a type of the sheets for use such as recording mediums. For example, in the case where the type of the sheets for use is thick paper (with a basis weight of 105 g/m2 or more), stiffness of the sheets becomes strong. Accordingly, there is a fear that the leading edges of the sheets may collide with a return guide member, and the sheets may not be nipped between the aligning roller and the process tray, causing a conveyance failure. In the case where the type of the sheets for use is coat paper onto which a coating material such as a resin is applied, the sheets become prone to stick on one another by the coating material. Accordingly, there is a fear that conveyance performance for the sheets may become poor, and the alignment of the sheets may turn to a disorder state.